Disposal of low-level nuclear wastes require that the waste be placed in a container suitable for burial. If the ultimate disposal site is not located at the generation point of such wastes, further container requirements are imposed to meet normal and accident transportation conditions.
One method of meeting these dual requirements is to design a single container capable of achieving the criteria established for both transport and burial. The stringent transportation requirements, however, dictate the use of a sturdy and expensive steel shell that would serve its purpose only once before being buried.
A more practical method of meeting the short term transportation and long term burial needs for nuclear waste disposal is to utilize separate burial containers and transportation casks. A container adequate for burial at the disposal site is placed within the transportation cask during handling and shipping, then is removed for burial at the disposal site, freeing the cask for reuse.
This burial container, sometimes referred to as a liner, must have an opening large enough to accommodate any apparatus that has to be inserted into the liner to process the waste, such as removing water from the slurry before shipment, as well as allowing human access for positioning of this apparatus. For this reason the prior art typically used a closure system with a plug or cap covering an opening in one end of a generally cylindrical burial container that was as large as the end of the container itself. Because metal containers will not typically withstand the environment of long-term burial, increasing use has been made of plastics. Burial containers, or liners, are often made of a high density plastic which is rotationally molded into the desired shape. Because it is undesirable to have joints in this material, elements of a closure system must be capable of being fabricated in one piece by the rotational molding process. In order to avoid tearing any type of seal or gasket in a container employing a screw type closure, a seal or gasket was first placed around the perimeter of the opening of the container. A stationary member was placed over the gasket then a screw type cap would bear down upon the stationary member and thereby seal the container.
It would be preferred, however, to have a smaller opening in which to add the waste or waste slurry. Having the open end of the container partially closed stabilizes any internal apparatus and lessens the likelihood of accidental spillage.